1. Field of the Invention
The present invention relates to a magnetic disk apparatus for writing/reading data on a magnetic disk and more particularly to a magnetic disk apparatus called a hard disk apparatus or a Winchester type disk drive apparatus.
2. Description of the Prior Art
There is a magnetic disk apparatus adapted such that a magnetic disk made of a hard disk type carrier with a magnetic recording layer formed on the surface thereof is rotated in a high speed therein, air is introduced between its slider formed integral with a magnetic head and the magnetic disk, whereby the magnetic head is floated over the magnetic disk and allowed to write data on the magnetic recording layer or read data written on the magnetic recording layer.
The magnetic disk apparatus of the described type (hereinafter to be called the hard disk apparatus) is principally made up of a magnetic disk provided with a recording region thereon within a predetermined width in its radial direction, a slider formed integral with a magnetic head whose core is placed in a coil, a spindle motor for rotationally driving the magnetic disk, a head drive mechanism for shifting the magnetic disk to a desired track position of the magnetic disk, and a housing for housing these components.
As an example of the mentioned type of the hard disk apparatus, there is one which is disclosed in Publication of European Patent Application No. 0 162 614. The invention, in an apparatus for supporting a transducer in the operating and sensing position over a recording medium, comprising a slider having a transducer attached thereto and having a main axis extending virtually tangent to the track to be read at the center of the recording medium, an arm assembly movable around a pivot, and suspension means attached to the arm assembly and the slider for holding the slider on the arm assembly so that the main extra extends through the pivot.
And it is disclosed therein that, in order to maintain the alignment of the transducer gap with the slider which carries the transducer tangent to the track, it is attempted that the relative angle between the tangent at the point on the track to be read and the main axis of the transducer is kept within a small range of variation as the head moves from the innermost to the outermost track, and to achieve this it is designed such that the angle between the main axis of the slider and the tangent to the innermost or outermost track will not be greater than 13 degrees.
Further, in order to minimize the head/track angle while providing the maximum arm stiffness with minimum inertia, two arms rotating around the common junction point of the two arms are used. These two arms are mounted at an acute angle. The distal end of the first arm is stepped by a stepping motor connected to the end of the arm. The distal end of the second arm carries the slider and transducer.
In the hard disk apparatus as described above, however, since the circumferential speed of the magnetic disk is larger on the outer circumferential side than on the inner circumferential side, in the case, for example, where the lengthwise direction of the slider is arranged virtually perpendicular to the radial direction of the magnetic disk, the floating height of the slider becomes larger at its outer edge to face on the outer circumference of the magnetic head than at its inner edge facing on the inner circumference. If, in this way, the slider is floated and inclined to the inner circumferential side, in the case where the circumferential speed at the innermost portion of the recording region becomes smaller as the magnetic disk is made smaller along with the development of higher recording density, that is, the floating height of the slider becomes very small at the portion under consideration, there arises a problem that the inner edge of the slider would collide with the surface of the magnetic disk in rotation thereby to damage the recording layer.
And, even if arrangement is made as in the above described hard disk apparatus such that the relative angle between the tangent at the point on the track to be read and the transducer, that is, the main axis of the slider, is kept within a small range of variation as the head moves from the innermost to the outermost track, and to achieve this, if it is designed such that the angle between the main axis of the slider and the tangent to the innermost or outermost track will not be greater than 13 degrees, there still is estimated totally 25 degrees of variation. Thus, in the case where the recording density is made higher, the detection output becomes smaller, and a problem is encountered in reading/writing.